In Word 2007 there is no Format menu, or no main menu bar at all, for that matter.

To change the defaults, do the following: Create a new, blank document, for example by pressing Ctrl+N. In the Styles pane (Ctrl+Alt+Shift+S), click the Manage Styles button. On the Set Defaults tab, make the desired changes. Select "New documents based on this template" and then click OK.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional